Friday, January 30, 2009

Greenhouse - Thrips, Thrips, Thrips

Thrips are a very important pest of greenhouse crops, largely because they spread viruses. Control can sometimes be difficult and they can become resistant to insecticides. The following is a great article on the subject from the University of Maryland.

Thrips Control

For the last 10 years many growers have been relying on spinosyn materials (Conserve) to control thrips in greenhouses. We have been warning growers not to rely on just one product to control this pest group because of chance of development of resistance. The resistance problem is being detected in greenhouses in North America. Dow AgroScience voluntarily suspended the sale and use of spinosyn insecticides in Broward and Palm Beach County in Florida as of August 14, 2008. This is a warning shot over the bow of the boat. It would be best to look for alternative control measures.

Early in the season:

In January through April thrips are generally present at relatively low numbers in most greenhouses unless you maintained a large weed population under your bench or maintained stock plants in the greenhouse loaded with thrips over the winter. When populations are low, usually measured by 1 - 2 adult thrips per sticky card, it would be best to use one of the neem insecticides such as Azatin, Neemix, or Aza-Direct mixed with BotaniGard or neem insecticide mixed with Naturalis-O can give good control when a thrips population is relatively low.

Here are some of the products that can be used to rotate between to control thrips:

􀂃 Abamectin
􀂃 Acephate (Orthene)
􀂃 Bifenthrin (Talstar)
􀂃 Chlorfenapyr (Pylon) (5 oz/100 gallons for low populations. For high populations use 10 -15 oz/100 gallons)
􀂃 Fluvalinate (Mavrik)
􀂃 Kinoprene (Enstar II)
􀂃 Methiocarb (Mesurol)
􀂃 Novaluron (Pedestal)
􀂃 Spinosad (Conserve – Dow Agro Science))
􀂃 Pyridalyl (Overature – Valent Company)

Overture 35 WP (active ingredient pyridalyl) by Valent Company can be used to target two pests in greenhouses - thrips and caterpillars. Overture was labeled for use in greenhouses in 2008. This material works by contact action and has translaminar properties. It is applied as a foliar spray. The label rate for thrips is 8 oz per 100 gallons and it has a 12 hour Re-entry Interval (REI). One thing we have noticed with the product is that control of thrips is often not seen for 7 to 14 days after treatment. Overture should be considered most effective when used as a preventative treatment or as a rotation product. Overture should be a good product to use in rotation with Conserve, Pylon and other thrips insecticides

Reprinted from the January 23, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report, University of Maryland Cooperative Extension, Central Maryland Research and Education Center

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